Metal powders are manufactured by the various methods, and in their properties such as particle shape, particle size, purity etc., there are large differences caused by the manufacturing methods. In this article the latest technical trends in addition to the manufacturing methods, the properties and the applications of non-ferrous metal powders are described. Especially in the field of copper-base metal powders, in place of the conventional Cu-Sn, or Cu-Zn system powder, new metal powder such as Cu-Al, or Cu-Ni-Sn system which has high performances of high strength and high corrosion resistance has been developed and put on the market. And with the progress of new metal forming technologies such as additive manufacturing (A.M), the new copper-base metal powder such as Cu-Cr or Cu-Zr system which has not been applied in the conventional powder metallurgy processes has been newly developed. In future, with the progress of the metal powder manufacturing technologies in cooperation with that of new metal forming technologies, the new markets in the field of powder metallurgy will be cultivated.
An electronic fuel injection system of automobiles have been commercialized at the end of 1960’s, they have been adopted as environmental measures for many automobiles and motorcycles. In recent years, metal injection molding (MIM) has been adopted as a process for manufacturing a solenoid valve which is a component of an electronic fuel injector, and PB permalloy components have been commercialized. However, Ni, an element of PB permalloy, is expensive material, making it difficult to produce the fuel injector component at a low cost. As a solution to this problem, we studied the magnetic properties of Fe-Cr-Si soft magnetic alloys by MIM process. These results revealed that the magnetic properties were improved by reducing Cr content. However, reducing Cr content is expected to reduce corrosion resistance of the alloys. In this study, Fe-Cr-Si-Mo alloy specimens containing Mo to improve corrosion resistance are manufactured by MIM process, and we investigated the magnetic properties and corrosion resistance. These results revealed that Fe-10Cr-3Si-2Mo alloy is a material with excellent magnetic properties and corrosion resistance.
The presence of pores in gas-atomized alloy powders induces a significant deterioration in the properties of the final product. However, there is no established technique to quantitatively analyze the porosity of gas-atomized powders. In this study, the pores in gas-atomized amorphous Fe76Si9B10P5 powder particles prepared under different atomization conditions were analyzed in detail using synchrotron radiation X-ray computed tomography. This technique allowed the detection of small pores with diameters below 10 µm. It also enabled the quantification of the porosity; thus, the pore diameter and volume ratio under different atomization conditions were determined. The volume ratio of the pores with the use of low-pressure Ar as the atomization gas was lower than that with the use of high-pressure Ar. The use of a low-pressure gas during spraying induced an increase in the diameter of the powder particles, thereby resulting in the presence of numerous irregular-shaped particles. The results of X-ray diffraction confirmed the partial precipitation of a crystalline phase with a decrease in the cooling rate. The use of 3 or 7% Ar–H2 mixtures as the atomization gas induced a decrease in the number and volume of pores, without affecting the particle size and cooling rate. The presence of H2 as a reducing gas suppressed the surface oxidation of the droplet during the atomization of the molten-metal stream, which allowed trapped gas bubbles to be efficiently removed before solidification.
The 47.4 vol% TiC-44.2 vol% Ti- 8.4 vol% W alloy was stronger than TiC-Ti-Mo alloy because the TiC particle size was smaller than that of the TiC-Ti-Mo alloy, however its corrosion resistance was inferior to the TiC-Ti-Mo alloy. The additive element for maintaining high strength needs to have the effect of forming βTi phase that promotes sintering and reducing the diameter of TiC particles. Mo and V are candidate for additive elements. Mo improves corrosion resistance more than V does. Therefore, a part of W was replaced with Mo, and the mechanical properties and corrosion resistance were investigated. It was found that 20 vol% Mo / (Mo + W)-added alloy excels in strength and corrosion resistance. The alloy sintered at 1573 K and HIP-treated showed the highest bending strength of 0.82 GPa with the hardness of HRC 68.2. It was confirmed that there is a correlation between the fracture origin size that caused the fracture of these test pieces and the fracture stress acting on the fracture. The high strength was obtained due to two effects: the alloy matrix strength was improved by the refinement of the microstructure, and the fracture origin size was reduced by the HIP treatment.